The present invention relates to an improved fuel vaporizing apparatus suitable for vaporing the liquid fuel or fuel-air charge for an internal combustion engine or gas turbine prior to its introduction into said engine or gas turbine, comprising such an apparatus and to automotive vehicles which comprise such an internal combustion engine or gas turbine having said apparatus.
The conventional spark-ignition engine relies on a carburetor to mix a desired proportion of a volatile fuel with the inlet air. For complete combustion of the fuel-air mixture the fuel needs to be uniformly dispersed in the air. Such a uniform mixture is seldom if ever obtained in practice with a conventional carburetor, and manifold fuel injection offers only marginal improvement.
In the conventional gas turbine a uniform fuel-air mixture (and uniform turbine entry temperature) is equally hard to achieve.
According to the inventions disclosed in U.S. Pat. No. 3,763,838 and U.S. patent applications Ser. No. 461,180 filed Apr. 15, 1974 and Ser. No. 461,174 filed Apr. 15, 1974, fuel vaporizing devices suitable for vaporizing the liquid fuel charge for an internal combustion engine or gas turbine prior to its introduction into said engine or gas turbine, and prior to or after mixing of the fuel with the main stream of combustion air, comprise one or more heat pipes, each of which is in the form of a sealed vessel containing a heat transfer fluid and is so constructed that in operation the heat transfer fluid in the said heat pipe or heat pipes is evaporated in the so-called heat-receiving zone of the heat pipe by heat received from the exhaust gases of the said engine or of the said gas turbine, and condensation of the said evaporated heat transfer fluid takes place by discharging heat for the evaporation of fuel to be combusted in the so-called fuel vaporizing zone of the heat pipe where the fuel is vaporized.
The use of one or more heat pipes enables heat to be supplied to the fuel or fuel-air mixture within a restricted temperature range virtually regardless of the rate at which the fuel is demanded. Furthermore, at start-up the heat pipe or pipes reach their operating temperature very much more quickly than a solid heat conductor.
The heat transfer fluid present in said heat pipe or pipes preferably has a boiling point at atmospheric pressure up to 400.degree.C.
As the heat demanded from the heat pipe can vary considerably, surplus heat can be removed by additional cooling means. These can, e.g., consist of a honeycomb or a multitubular condenser in the upper part of the heat pipe which, e.g., is cooled with the aid of the cooling system of the engine. When additional cooling means are used a separate return line is advantageously provided for returning heat transfer fluid condensed by these means to the liquid bulk of that fluid in the heat pipe, without contacting this condensed heat transfer fluid with the fuel vaporizing section or the rising vapor of the heat transfer fluid. It is also possible to cool the upper part of the heat pipe itself by circulating coolant from the cooling system of the engine therethrough. Air may also be used as additional cooling agent.
The additional cooling means discussed do not show a great flexibility and may not be able in all cases to accept sufficient heat from the vapor of the heat transfer fluid to condense such an amount of the latter vapor that no undesired high pressure in the heat pipe is built up.
Moreover leakages in the heat pipe through which heat transfer fluid is removed therefrom are not easily discerned in the heat pipe systems proposed hitherto.
Furthermore, it is considered as a drawback that in the known devices two liquid-containing systems are present in one engine, viz the cooling system and the heat pipe, which are not connected with each other.